When a memory device, such as CXL1.1 type3 memory, is emulated as
normal memory (E820_TYPE_RAM), the memory device is indistinguishable
from normal DRAM in terms of memory tiering with the current implementation.
The current memory tiering assigns all detected normal memory nodes
to the same DRAM tier. This results in normal memory devices with
different attributions being unable to be assigned to the correct memory tier,
leading to the inability to migrate pages between different types of memory.
https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/
This patchset automatically resolves the issues. It delays the initialization
of memory tiers for CPUless NUMA nodes until they obtain HMAT information
and after all devices are initialized at boot time, eliminating the need
for user intervention. If no HMAT is specified, it falls back to
using `default_dram_type`.
Example usecase:
We have CXL memory on the host, and we create VMs with a new system memory
device backed by host CXL memory. We inject CXL memory performance attributes
through QEMU, and the guest now sees memory nodes with performance attributes
in HMAT. With this change, we enable the guest kernel to construct
the correct memory tiering for the memory nodes.
-v5:
Thanks to Ying's comments,
* Add comments about what is protected by `default_dram_perf_lock`
* Fix an uninitialized pointer mtype
* Slightly shorten the time holding `default_dram_perf_lock`
* Fix a deadlock bug in `mt_perf_to_adistance`
-v4:
Thanks to Ying's comments,
* Remove redundant code
* Reorganize patches accordingly
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v3:
Thanks to Ying's comments,
* Make the newly added code independent of HMAT
* Upgrade set_node_memory_tier to support more cases
* Put all non-driver-initialized memory types into default_memory_types
instead of using hmat_memory_types
* find_alloc_memory_type -> mt_find_alloc_memory_type
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v2:
Thanks to Ying's comments,
* Rewrite cover letter & patch description
* Rename functions, don't use _hmat
* Abstract common functions into find_alloc_memory_type()
* Use the expected way to use set_node_memory_tier instead of modifying it
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v1:
* https://lore.kernel.org/lkml/[email protected]/T/#u
Ho-Ren (Jack) Chuang (2):
memory tier: dax/kmem: introduce an abstract layer for finding,
allocating, and putting memory types
memory tier: create CPUless memory tiers after obtaining HMAT info
drivers/dax/kmem.c | 20 +-----
include/linux/memory-tiers.h | 13 ++++
mm/memory-tiers.c | 117 +++++++++++++++++++++++++++++++----
3 files changed, 119 insertions(+), 31 deletions(-)
--
Ho-Ren (Jack) Chuang
Since different memory devices require finding, allocating, and putting
memory types, these common steps are abstracted in this patch,
enhancing the scalability and conciseness of the code.
Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
---
drivers/dax/kmem.c | 20 ++------------------
include/linux/memory-tiers.h | 13 +++++++++++++
mm/memory-tiers.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 47 insertions(+), 18 deletions(-)
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 42ee360cf4e3..01399e5b53b2 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -55,21 +55,10 @@ static LIST_HEAD(kmem_memory_types);
static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
{
- bool found = false;
struct memory_dev_type *mtype;
mutex_lock(&kmem_memory_type_lock);
- list_for_each_entry(mtype, &kmem_memory_types, list) {
- if (mtype->adistance == adist) {
- found = true;
- break;
- }
- }
- if (!found) {
- mtype = alloc_memory_type(adist);
- if (!IS_ERR(mtype))
- list_add(&mtype->list, &kmem_memory_types);
- }
+ mtype = mt_find_alloc_memory_type(adist, &kmem_memory_types);
mutex_unlock(&kmem_memory_type_lock);
return mtype;
@@ -77,13 +66,8 @@ static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
static void kmem_put_memory_types(void)
{
- struct memory_dev_type *mtype, *mtn;
-
mutex_lock(&kmem_memory_type_lock);
- list_for_each_entry_safe(mtype, mtn, &kmem_memory_types, list) {
- list_del(&mtype->list);
- put_memory_type(mtype);
- }
+ mt_put_memory_types(&kmem_memory_types);
mutex_unlock(&kmem_memory_type_lock);
}
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 69e781900082..a44c03c2ba3a 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -48,6 +48,9 @@ int mt_calc_adistance(int node, int *adist);
int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
const char *source);
int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
+struct memory_dev_type *mt_find_alloc_memory_type(int adist,
+ struct list_head *memory_types);
+void mt_put_memory_types(struct list_head *memory_types);
#ifdef CONFIG_MIGRATION
int next_demotion_node(int node);
void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -136,5 +139,15 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
{
return -EIO;
}
+
+struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+{
+ return NULL;
+}
+
+void mt_put_memory_types(struct list_head *memory_types)
+{
+
+}
#endif /* CONFIG_NUMA */
#endif /* _LINUX_MEMORY_TIERS_H */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 0537664620e5..974af10cfdd8 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -623,6 +623,38 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
}
EXPORT_SYMBOL_GPL(clear_node_memory_type);
+struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+{
+ bool found = false;
+ struct memory_dev_type *mtype;
+
+ list_for_each_entry(mtype, memory_types, list) {
+ if (mtype->adistance == adist) {
+ found = true;
+ break;
+ }
+ }
+ if (!found) {
+ mtype = alloc_memory_type(adist);
+ if (!IS_ERR(mtype))
+ list_add(&mtype->list, memory_types);
+ }
+
+ return mtype;
+}
+EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
+
+void mt_put_memory_types(struct list_head *memory_types)
+{
+ struct memory_dev_type *mtype, *mtn;
+
+ list_for_each_entry_safe(mtype, mtn, memory_types, list) {
+ list_del(&mtype->list);
+ put_memory_type(mtype);
+ }
+}
+EXPORT_SYMBOL_GPL(mt_put_memory_types);
+
static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
{
pr_info(
--
Ho-Ren (Jack) Chuang